1. Field of the Invention
The present invention relates to a substrate processing system, and in particular to a substrate processing system having an etching apparatus having therein an electrostatic chuck that electrostatically attracts a substrate.
2. Description of the Related Art
A substrate processing system for forming wiring grooves or via holes in a desired pattern using plasma on a front surface of a wafer as a substrate is comprised of a photoresist apparatus for forming a resist film in a desired pattern on the front surface of the wafer, an etching apparatus for subjecting the front surface of the wafer to etching processing such as RIE (reactive ion etching) processing, and a washing apparatus for removing the resist film. Here, the photoresist apparatus has a coater that coats a photosensitive resin onto the front surface of the wafer, a stepper that exposes the photosensitive resin, and a developer that removes uncured photosensitive resin from the front surface of the wafer. Moreover, the etching apparatus has a housing chamber that houses the wafer and in which plasma is produced, and an electrostatic chuck that is disposed in the housing chamber and electrostatically attracts the wafer thereto while the wafer is being subjected to the etching processing (see, for example, Japanese Laid-open Patent Publication (Kokai) No. 2005-347620).
Using the stepper, the photosensitive resin on the front surface of the wafer is irradiated with UV light or the like in a desired pattern. In recent years, as the desired pattern has become finer, UV light of a shorter wavelength, for example a wavelength of 193 nm, has come to be used. If the wavelength is shorter, then the depth of focus is also reduced, and hence the tolerances on the flatness and the inclination of the wafer are reduced. Moreover, with such a stepper, a plurality of pin-like projections support a rear surface of the wafer, and hence the flatness and the inclination of the wafer are greatly affected by scratches, foreign matter etc. on the rear surface of the wafer.
Furthermore, to realize a complex semiconductor device wiring structure or electrode structure on a wafer, the wafer must be subjected to etching processing in the substrate processing system repeatedly, and each time the etching processing is carried out, the wafer is electrostatically attracted to the electrostatic chuck. The surface of the electrostatic chuck is covered with yttria (Y2O3), and hence the rear surface of the attracted wafer, which is made of silicon (Si), may be scratched. Moreover, foreign matter present on the surface of the electrostatic chuck may be transferred onto the rear surface of the wafer.
However, although foreign matter attached to the rear surface of a wafer can be removed by wet washing using a washing liquid or the like, no method is known for effectively removing scratches from the rear surface of a wafer. There is thus a fear that it may become impossible to maintain the flatness of a wafer within the allowed tolerance due to such scratches on the rear surface of the wafer. It is thus necessary to prevent the rear surface of a wafer from being scratched when the wafer is attracted by the electrostatic chuck.